There are metallic filaments out there, but I expect the results may not be what you seek. Those that I've seen appear to require high levels of careful detailed sanding, followed by equally careful detailed polishing and yet, the grain of the plastic is easily seen.

If you are able to create a model or find one that works as a tie clip, you can perform what is called electroforming. A conductive paint is applied and dried and the item is immersed in metallic solution while a current is applied. The metal is transferred to the conductive paint during the process. If you use a solution of silver, you get a silver layer. Use a copper or nickel solution and that's the layer that is generated. Nickel will be the lowest cost shiny silver option, while silver and gold are going to be way up there!

Use search terms "electroforming 3d models" or "electroforming 3d prints" to see many resources for performing this type of project.

One of them is an instructables for a ring:

https://www.instructables.com/id/How...roform-A-Ring/